Where you have the double connector on one side of the light casing touch the new wire to one terminal and then the other one, the one that works with the door open is the right one.
The other terminal will light the footwell lights no immediately as it's the permanent live feed to the on switch of the light fitting.
I'll try to suss the wires and terminals more accurately when I'm home.
Currently running the dogs on the moors.

Believe it will be the terminal laying flat (with arrow) on the left of the photo you need to connect to, check like i said above and you'll know for sure.
If the lights go on immediately without moving switches or with the door being opened then it will be the other one you need.

Chees artscot, electrics not my forte I'm afraid, started from scratch with the footwell lighting as had nothing there, managed to fit the bulb holders and all wiring up the a pillar to the interior light.....then I was stumped!! Lol